The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
In a vehicle in which an automated manual transmission (AMT) or a dual clutch transmission (DCT) as a transmission is mounted and power sources such as an engine and a motor transfer power to the transmission through the dry clutch, a control of the dry clutch is an important factor having a significant effect on drivability of the vehicle.
In particular, unlike the existing torque converter, the dry clutch itself does not have a damping function, and therefore a shock is highly likely to be generated upon engagement and disengagement of the clutch. As a result, the proper clutch control becomes an important factor for smooth launching or shifting of a vehicle.
For reference, unless mentioned separately, the term clutch herein refers to the dry clutch forming a dual clutch of the DCT or a clutch of the AMT.
The term clutch control substantially refers to a control of a clutch torque, i.e. a torque transferred by the clutch. Basically, the sudden change in the clutch torque (also referred to as ‘jerk’) is a main cause of causing the shock of the clutch, and therefore the control of the clutch is performed to avoid the sudden change in the clutch torque. To this end, a clutch control torque directly used to control a clutch actuator actually controlling the clutch is processed so that the clutch control torque is smoothly changed.
That is, a curved line drawn by the clutch control torque over time preferably forms a smooth profile.
For this reason, for the existing clutch control, a filter is configured to limit a variation of the clutch control torque per control unit time, and to limit even a change in jerk that is a differential value of the variation of the clutch control torque, and therefore even the change in the clutch control torque may form the smooth profile. In detail, the jerk of the clutch control torque is uniformly limited to a predetermined level to suppress the clutch control torque from being suddenly changed.
FIG. 1 illustrates the existing process of changing a creep driving state of a vehicle to a launching state by pressing, by a driver, an accelerator pedal and illustrates a process of controlling a clutch to set a launching target torque that is a clutch target torque by slightly reducing a clutch torque to induce a smooth increase in an engine speed and then increasing the clutch torque to launch a vehicle depending on an operation of the accelerator pedal by a driver and follow up the set launching target torque.
The launching target torque is calculated to a degree desired to smoothly launch a vehicle depending on the manipulated quantity of the accelerator pedal by driver. As such, if the clutch control is performed based on the launching target torque calculated in consideration of only the launching condition of the vehicle, a shock is highly likely to be applied to the vehicle due to the sudden change in the clutch torque. Therefore, the clutch control torque as illustrated is calculated by performing the filtering to limit the jerk of the launching target torque, and as a result the clutch actuator is substantially operated depending on the clutch control torque.
In this case, in the process of slightly reducing the launching target torque and then increasing the launching target torque again to induce the smooth increase in the engine speed, if the launching target torque is filtered, the jerk of the clutch control torque is limited to a predetermined level, and thus the filtered clutch control torque is reduced in response to the launching target torque and then is not suddenly increased in response to the launching target torque but is changed to be increased with the profile drawing the smooth curved line as illustrated by an arrow. In this case, we have found that, although the profile of the clutch control torque is smoothly changed, the clutch control torque actually controlling the clutch does not properly follow up the launching target torque that is a control target and therefore a shock is generated, which may be appreciated from FIG. 1 that the vibration of the accelerator sensor signal is generated.
The contents described as the related art have been provided only for assisting in the understanding for the background of the present disclosure and should not be considered as corresponding to the related art known to those skilled in the art.